Abstract

Ulcerative colitis(UC) is a kind of chronic inflammatory bowel disease, with the etiology and pathogenesis still unknown.Most professional specialists thought that it is a kind of autoimmune disease. It was suggested that the transcripition factor NF-kB plays an important role in the inflammatory process of chronic inflammatory bowel disease. The active form of NF-kB is a heterodimer that is frequently composed of the p65 and p50 subunit. NF-kB activation occupy a critical position for the initiation and perpetuation of intestinal inflammation.In nonstimulated cells, NF-kB is sequestered in the cytoplasm as a latent, inactive complex bound to inhibitory proteins termed IkB. Many different stimuli activate NF-KB,including cytokines such as tumor necrosis factor(TNF)and interleukin (IL)-l, lipopolysaccarides,bacterial and viral infections, activators of protein kinase C, and oxidants. Glucocorticoids and 5-aminosalicylic acid(5-ASA)are widely used for the treatment of inflammatory bowel disease such as ulcerative colitis and Crohn’s disease. Its mechanisms is that they may inhibit the activations of transcription factor NF-kB in inflamed mucosa of patients with ulcerative colitis. Glucocorticords are widely used as immunosuppressive agents in ulcerative colitis(UC). However,although glucocorticoids are highly effective, up to one fourth of patients with ulcerative colitis fail to respond to steroids. The molecular mechanism underlying steroid unresponsiveness remains unknown.Our study was designed to investigate the role of NF-kB expression in UC pathogenesis and in steroid resisance.Because the activation of NF-kB is regulated at the posttranslational level, it cannot be assessed by measuring mRNA or proteins level in tissue biopsies. We therefore employed an antibody that detects the nuclear location sequence (NLS) of the p65 subunit of NF-kB, which is normally masked by bound IkB. Thus, the antibody exclusively detects activated NF-kB and allows the investigation of its activation state by immunohistochemistry in tissue sections. Our results suggest that NF-kB activation may be involved in UC, and there are significant difference in the expression of NF-kB between the steroid-resistant patients and steroid-sensitive patients after steroid treatment.MATERIALS AND METHODSChapter 1 STUDIES ON EXPRESSION OF NUCLEAR FACEOR- KAPPA B IN ULCERATIVE COLITIS PATHOGENESIS1. Patients:We investigated the activation of NF-kB in biopsies from 34 patients with an acute episode of ulcerative colitis from Oct 2002 to Aug 2004,in which have 20 male cases and 14 female cases. NF-kB activity was investigated in biopsies from various regions of the affected mucosa using an antibody against the NLS of p65 subunit of NF-kB. 26 cases of normal controls were investigated too.2. Reagents:The mouse monoclonal antibody, which selectively binds to the NLS sequence of the activated p65 NF-kB subunit, was purchased from santa Cruz Biotechnology.3. Immunohistochemical staining of tissue sections:Sections 4um thick were deparaffinized in xylene and rehydrated through degraded concentrations of ethanol.The expression of NF-kB p65 was examined in 60 cases of paraffin-embedded tissues by immunohistochemical methods, which were from endoscopic biopsies of 34 cases active UC and 26 cases normal controls.4. Statistical MethodsAll of the data were recorded and set up data bank which was performed statistical analysis by SPSS 10.0 software. The level of significance was a=0.05. Data bank was analyzed by t test and signed rank test.Chapter 2 STUDIES ON EXPRESSION OF NUCLEAR FACEOR- KAPPA B IN STEROID-RESISTANT ULCERATIVE COLITIS1. Patients:We investigated the activation of NF-kB in UC biopsies from 15 steroid-resistant patients, 20 steroid-sensitive patients with an acute episode of moderate or severe ulcerative colitis. Steroid-resistant patients failed to respond to glucocorticoids, whereas treatment of sensitive patients resulted in a complete remission, within 4 weeks. NF-kB activity was investigated in biopsies from various regions of the affected m